One grand challenge in neural stem cell research and regenerative medicine is the precise isolation and extraction of functional neural stem cells from adult brains. Neural stem cells (NSCs) are self-renewing and multipotent in nature, allowing cell replacement therapies for diseases in the nervous system, which are generally incurable at present. Currently, neural stem cells can only be obtained from foetal tissues or differentiated from other cell types as alternative sources. At present it is practically impossible to obtain neural stem cells directly from the patients themselves who are often adults. The objective of the present invention is to provide a method for extracting biological cells, particularly neural stem cells from a subject in which the aforesaid shortcomings are mitigated or at least to provide a useful alternative.